Binary To Octal Conversion | C Program

Binary to Octal conversion in C

There are two approaches of converting an Binary Number into a Octal Number like

  • Converting Binary to Decimal and then Decimal to Octal
  • By grouping Binary Number into Groups of 3 digits/bits and then converting to Octal

We will cover both approaches in this post

binary to decimal in c

Method 1:-

We will first convert the Binary number into Decimal and then convert the Decimal number into Octal

Make sure that you have gone through these approaches below –

  1. Binary to Decimal Conversion
  2. Decimal to Octal Conversion

Method 1 Code

Run
#include<stdio.h>
#include<math.h>

// function to convert binary to octal
void convert(long long num)
{
    int octalDigit = 0, count = 1, i = 0, pos = 0;
    int octalArray[32] = {0};

    while(num != 0)
    {
        int digit = num % 10;
        
        octalDigit += digit * pow(2, i);
        i++;
        num /= 10;
        
        // placing current octalsum for 3 pair in array index position
        octalArray[pos] = octalDigit;
        
        // whenever we have read next 3 digits
        // setting values to default
        // increasing pos so next values can be placed at next array index
        if(count % 3 == 0)
        {
            octalDigit = 0;
            i = 0;
            pos++;
        }
        count++;
    }
        
    // printing octal array in reverse order
    for (int j = pos; j >= 0; j--)
        printf("%d",octalArray[j]);

}

//main program
int main()
{
    // long used rather than int to store large values
    long long binary;
    
    printf("Enter binary number: ");
    scanf("%lld", &binary);
    
    convert(binary);
    
    return 0;
}

Output :

Enter binary number: 1010
Decimal : 10
Octal : 12

Method 2:-

Method 2 uses the concept of grouping 3 successive digits/bits of the binary number and calculating octal digits against each grouping

We use an additional array to store the octal digits at each index.

We will need to print the array in reverse to get actual octal equivalent.

Method 2 Code

Run
#include<stdio.h>
#include<math.h>
// function to convert binary to octal
void convert(long long num)
{
    int octalDigit = 0, count = 1, i = 0, pos = 0;
    int octalArray[32] = {0};

    while(num != 0)
    {
        int digit = num % 10;
        
        octalDigit += digit * pow(2, i);
        i++;
        num /= 10;
        
        // placing current octalsum for 3 pair in array index position
        octalArray[pos] = octalDigit;
        
        // whenever we have read next 3 digits
        // setting values to default
        // increasing pos so next values can be placed at next array index
        if(count % 3 == 0)
        {
            octalDigit = 0;
            i = 0;
            pos++;
        }
        count++;
    }
        
    // printing octal array in reverse order
    for (int j = pos; j >= 0; j--)
        printf("%d",octalArray[j]);

}

//main program
int main()
{
    // long used rather than int to store large values
    long long binary;
    
    printf("Enter binary number: ");
    scanf("%lld", &binary);
    
    convert(binary);
    
    return 0;
}

Output :

Enter binary number: 010101
25
Binary to Octal in C Program

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8 comments on “Binary To Octal Conversion | C Program”


  • Sahil

    #include
    #include
    int main()
    {
    int binary,rem,decimal=0,octal=0 ,weight=1,num;
    printf(“enter the binary number :\n”);
    scanf(“%d”,&binary);

    num=binary;

    while(num!= 0)
    {
    rem=num%10;
    decimal=decimal+rem*weight;
    weight=weight*2;
    num=num/10;
    }
    weight=1;
    rem =0;
    while(decimal!= 0)
    {
    rem = decimal%8;
    octal = octal+rem*weight;
    weight = weight * 10;
    decimal = decimal/8;
    }
    printf(“the binary number =%d and its octal number is=%d”,binary,octal);
    getch();
    return 0;

    }


  • Somnath

    #include
    int main()
    {
    int binary,decimal=0,octal=0,m=1,n=1;;
    scanf(“%d”,&binary);
    while(binary>0)
    {
    decimal=decimal+(binary%10)*m;
    m=m*2;
    binary=binary/10;
    if(m==8)
    {
    octal=octal+n*decimal;n=n*10;m=1;decimal=0;
    }
    }
    octal=octal+n*decimal;
    printf(“%d”,octal);
    return 0;
    }


  • Narahari

    This code is same as binary to decimal

    binary to octal is as follows:
    // Online C compiler to run C program online
    #include
    int binary2octal(int n);
    int binary2decimal(int n);
    int main()
    {
    int number,octal;
    printf(“enter binary number”);
    scanf(“%d”,&number);
    octal= binary2octal(number);
    printf(“bin to octal of %d is %d”,number,octal);

    }
    int binary2octal(int number)
    {
    int octal=0,value,i=1,lastdigit;
    while(number !=0)
    {
    lastdigit=number%1000;
    value= binary2decimal(lastdigit);
    octal=octal+value*i;
    i=i*10;
    number=number/1000;
    } return octal;
    }
    int binary2decimal(int number)
    {
    int dn=0,base=1,rem;
    while(number!=0)
    {
    rem=number%10;
    dn=dn+rem*base;
    base=base*2;
    number=number/10;
    }
    return dn;
    }


  • Ravi kumar

    #include
    #include
    int convert(long long bin);
    int main() {
    long long bin;
    printf(“Enter a binary number: “);
    scanf(“%lld”, &bin);
    printf(“%lld in binary = %d in octal”, bin, convert(bin));
    return 0;
    }

    int convert(long long bin) {
    int oct = 0, dec = 0, i = 0;

    // converting binary to decimal
    while (bin != 0) {
    dec += (bin % 10) * pow(2, i);
    ++i;
    bin /= 10;
    }
    i = 1;

    // converting to decimal to octal
    while (dec != 0) {
    oct += (dec % 8) * i;
    dec /= 8;
    i *= 10;
    }
    return oct;
    }


  • Kritika pandit

    This code is wrong as it converts binary to decimal only
    when input is 10101001 the above code prints 169 as its octal no.which is wrong.


        • Shailesh

          #include
          #include
          int main()
          {
          int n,rem,d=0,b=0;
          scanf(“%d”,&n);
          while(n>0){
          rem=n%10;
          d=d+(pow(2,b)*rem);
          b++;
          n/=10;
          }
          int o=0,i=1;
          while(d!=0){
          o=o+((d%8)*i);
          d=d/8;
          i=i*10;

          }
          printf(“%d”,o);
          return 0;
          }

          0